A radio-thermometer system, and a method for measuring electromagnetic energy radiated from an interior of a human body, includes an antenna for receiving thermal energy radiated from a target object having a temperature to be measured, first and second noise sources, which are maintained at different temperatures in order to obtain a reflection coefficient of an interface between the antenna and the target object, a first switch for periodically switching between outputting the first or second noise source, a circulator for adding a signal received by the antenna to a reflective wave output from the first switch, and for transmitting an addition result, third and fourth noise sources, which are maintained at different temperatures, a second switch for periodically switching between outputting an output of the third noise source, the circulator, and the fourth noise source, and an amplifier for amplifying an output of the second switch.